The present invention relates to a method of handling a large structure when a large component of a nuclear power plant, such as a rector pressure vessel, a large structure member in a reactor, etc., is replaced; or decommissioning of the nuclear power plant is conducted.
A nuclear power plant is designed so that it has a sufficient margin to its life time which was required on the occasion of its construction. Further, the life time of the nuclear power plant can be extended by exchanging life-expired components/parts of the plant. In the case where a large structural component or part to be exchanged is moved into or out of a reactor building, there is sometimes a problem in that the size of a conventional entrance provided in the reactor building is too small. In this case, it is necessary to provide an aperture portion at the roof of the reactor building, through which the large structure can be passed, (hereafter, simply referred to as an aperture portion).
Here, Japanese Patent Application Laid-Open Hei 8-262190 discloses a relevant method in which, when a reactor pressure vessel (hereafter referred to as a RPV) of a large structure, is exchanged, a block of a size such that which can pass the structure through it, is cut out from the roof of the reactor building by a cutting machine using a laser beam, and the cut-out block is lifted up by a crane.
When a large structure such as a RPV is exchanged, fuel assemblies, components, and etc., are moved by using a roof crane in an operating floor of a reactor building. Therefore, it is important to reduce the stopping time of a nuclear power plant by adjusting the proceeding of work of moving components and work of providing/occluding an aperture portion at the roof of the reactor building.
Generally, a roof of a reactor building has a multilayer structure composed of a steel framework of truss structure, which reinforces the reactor building, a deck plate covering the steel framework, and a concrete layer of 100-300 mm thickness, which is made up by pouring concrete onto the deck plate. Here, it is an important subject that the work of providing/occluding an aperture portion, which is performed at the upper position of the operating floor, does not interfere with work of moving fuel assemblies, components, etc.
However, Japanese Patent Application Laid-Open Hei 8-262190 does not specifically disclose how the work of providing/occluding an aperture portion is performed. Accordingly, by the method disclosed in this document, it is inevitable that the work of providing/occluding an aperture portion interferes with the work of moving fuel assemblies, components, etc. Further, if the work of providing/occluding an aperture portion is performed over a fuel pool in which fuel assemblies are stored, extraneous parts may fall into the fuel pool. Therefore, the work of providing/occluding an aperture portion must be performed after all fuel assemblies are taken out of the RPV. Consequently, processes of exchanging a large structure such as a RPV takes a long time.
An objective of the present invention is to provide a method of handling a large structure when carrying the large structure out/in through an aperture portion provided at the roof of a reactor building, which can reduce the time necessary to carry the large structure out/in.
To achieve the above objective, the present invention provides a method of handling a large structure in a reactor building in carrying the large structure out through an aperture portion provided at a roof of the reactor building, wherein an isolation chamber for isolating work of providing the aperture portion is installed on the roof before at least a part of work of handling fuel assemblies and at least a part of work of using a roof crane, and the work of providing the aperture portion is performed in parallel with at least a part of work of handling fuel assemblies and at least a part of work of using a roof crane.
Further, the present invention provides a method of handling a large structure in a reactor building in carrying the large structure out through an aperture portion provided at a roof of the reactor building, wherein work of carrying the large structure in is performed in a state in that a chamber for covering the aperture portion, which is installed for performing work of occluding the aperture portion independent of other work performed in the reactor building, is installed at the roof; and after the work of carrying the large structure in, at least a part of work of using a roof crane in the reactor building is performed in parallel with the work of occluding the aperture portion.
Furthermore, the present invention provides a method of handling a large structure in a reactor building in carrying the large structure out through an aperture portion provided at a roof of the reactor building, the method comprising the steps of: providing a chamber for covering the aperture portion provided at the roof so that work of providing the chamber for covering the aperture portion can be performed independent of other work performed in the reactor building, before at least a part of work of handling fuel assemblies and at least a part of work of using a roof crane in the reactor building; performing the work of providing the aperture portion in parallel with at least a part of the work of handling fuel assemblies and at least a part of work of using a roof crane in the reactor building; performing the work of carrying in the large structure; and performing work of occluding the aperture portion in parallel with at least a part of the work of handling fuel assemblies and at least a part of work of using a roof crane in the reactor building after the work of carrying the large structure in.
In accordance with the present invention, when work of carrying a large structure out/in through an aperture portion provided at the roof of a reactor building, since work of providing/occluding the aperture portion can be performed in parallel with a part of handling fuel assemblies and a part of work using a roof crane, the time of total work can be remarkably reduced.